As shown in FIG. 1, a pixel point of a conventional flat panel display includes three sub-pixels including red, green and blue (RGB). Each sub-pixel has a total of 256 gray levels from 0 to 255. Different colors are formed by combining different gray levels of the red, green and blue sub-pixels. With the development of a flat panel display, people demand more and more high definition of the flat panel display and more and more high resolution. This results in less and less aperture ratio of the flat panel display with the same size and less and less transmittance of a backlight thereof. Therefore, a present RGB model cannot satisfy the requirements of developing the flat panel display. An RGBW model is innovated from a basis of the conventional three basic colors RGB and adds a white sub-pixel. A transmittance of the white sub-pixel is three times of that of any one of the red, green and blue sub-pixels. Accordingly, a transmittance of an entire flat panel display can be efficiently increased.
As shown in FIG. 2, the pixel point including the red, green, blue and white sub-pixels requires a driving circuit to drive. The driving circuit according to RGBW comprises: a first driving lines 201, a second driving lines 202, a third driving lines 203, a fourth driving lines 204, a first switch K1, a second switch K2, a third switch K3 and a fourth switch K4, a control terminal of the first switch K1 connected to the first driving line 201, an input terminal of the first switch K1 connected to a driving signal source 205, another input terminal of the first switch K1 connected to the red sub-pixel, a control terminal of the second switch K2 connected to the second driving line 202, an input terminal of the second switch K2 connected to the driving signal source 205, another input terminal of the second switch K2 connected to the green sub-pixel, a control terminal of the third switch K3 connected to the third driving line 203, an input terminal of the third switch K3 connected to the driving signal source 205, another input terminal of the third switch K3 connected to the blue sub-pixel, a control terminal of the fourth switch K4 connected to the fourth driving line 204, an input terminal of the fourth switch K4 connected to a driving signal source 205 and another input terminal of the fourth switch K4 connected to the white sub-pixel.
When the first driving line 201 outputs a high voltage level, the second driving line 202 outputs a low voltage level, the third driving line 203 outputs a low voltage level and the fourth driving line 204 outputs a low voltage level, the first switch K1 is turned on, the second switch K2 is turned off, the third switch K3 is turned off and the fourth switch K4 is turned off. A driving signal from the driving signal source 205 is outputted to the red sub-pixel through the first switch K1 so the red sub-pixel generates a red light through a light generated by the backlight lamp.
When the first driving line 201 outputs a low voltage level, the second driving line 202 outputs a high voltage level, the third driving line 203 outputs the low voltage level and the fourth driving line 204 outputs the low voltage level, the first switch K1 is turned off, the second switch K2 is turned on, the third switch K3 is turned off and the fourth switch K4 is turned off. The driving signal from the driving signal source 205 is outputted to the green sub-pixel through the second switch K2 so the green sub-pixel generates a green light through the light generated by the backlight lamp.
When the first driving line 201 outputs the low voltage level, the second driving line 202 outputs the low voltage level, the third driving line 203 outputs a high voltage level and the fourth driving line 204 outputs the low voltage level, the first switch K1 is turned off, the second switch K2 is turned off, the third switch K3 is turned on and the fourth switch K4 is turned off. The driving signal from the driving signal source 205 is outputted to the blue sub-pixel through the third switch K3 so the blue sub-pixel generates a blue light through the light generated by the backlight lamp.
When the first driving line 201 outputs the low voltage level, the second driving line 202 outputs the low voltage level, the third driving line 203 outputs the low voltage level and the fourth driving line 204 outputs a high voltage level, the first switch K1 is turned off, the second switch K2 is turned off, the third switch K3 is turned off and the fourth switch K4 is turned on. The driving signal from the driving signal source 205 is outputted to the white sub-pixel through the fourth switch K4 so the white sub-pixel generates a white light through the light generated by the backlight lamp.
Therefore, driving the four sub-pixels including red, green, blue and white requires four driving lines, but a large area is occupied by the driving lines to decrease the aperture ratio of the flat panel display.